1. Field of the Invention
The present invention generally relates to image processing technology, and particularly relates to an image processing method to be employed in game applications of domestic game devices and computer games.
2. Description of the Related Art
As an application program of conventional domestic game devices, there is a soccer game. In this soccer game, the field line (white line) is configured from a plurality of polygons to which a white line texture has been affixed thereto. In this program, a viewpoint is defined in a global coordinate system, and the screen image of the line in the field of this coordinate system viewed from the viewpoint is subject to perspective transformation and drawn in the frame buffer. When the viewpoint is distant from the line and the angle of the viewpoint viewing the line is small in relation to the line, the line would become a one dot width or less due to the resolution of the display device in the game device, and there were inconveniences in that the line would become broken or displayed as dots on the screen.
In order to overcome this kind of problem, as disclosed in Japanese Patent No. 2955989, polygons of the line placed on the field are inclined to increase the area when viewed from the viewpoint.
Further, FIG. 8 is a diagram explaining why a linear object cannot be displayed accurately. Let it be assumed that eight triangular polygons are to be displayed closely as shown in FIG. 8(2). Each of the symbols □▪▴ illustrated in FIG. 8(1) represents one pixel on the screen. Since each of the triangles (1-8 in FIG. 8(2)) is disposed closely, the pixels of ▪ will overlap with the adjacent triangles. Whether to display the pixels of ▪ according to a certain algorithm is determined in order to avoid such overlap. As a result, there are cases where the edges of polygons are not represented properly. The ratio of pixels representing edges will increase pursuant to the decrease in the area of polygons, and the accuracy of the polygons will thereby deteriorate. Thus, elongated polygons are sometimes displayed as dots or not displayed at all.